Cold tolerance and water content of current-year red spruce foliage over two winter seasons

Red spruce (Picea rubens Sarg.) in high elevation forests of northeastern North America suffers from frequent and severe winter injury, leading to apical dieback, decreased growth, and high mortality. To examine the role of winter desiccation and freezing injury in winter damage, weekly assessments of cold tolerance and water content were made on current-year foliage collected from native red spruce trees at a high elevation site over two winter seasons. In both years, foliage maintained high water contents and adequate cold tolerance; nonetheless, slight to moderate injury was observed each year on some trees. Despite brief thaw periods each winter, no mid-winter dehardening sufficient to put foliage at risk of freezing injury was evident. These findings suggest that, at least in some years, winter injury to current-year red spruce foliage is produced by a mechanism other than desiccation or absolute low temperatures.     

Midwinter needle temperature and winter injury of montane red spruce

To assess the role of solar warming and associated temperature fluctuations in the winter injury of sun-exposed red spruce foliage, we used fine wire thermocouples to monitor midwinter needle temperature in the upper canopy of mature red spruce trees over two winters. In 1989-1990, 15-min mean temperatures were recorded for six needles in a single tree. In 1990-1991, 10-min mean temperatures of six needles in one tree, and 1-min mean temperatures of seven needles in a second tree were recorded during rapid temperature changes. Warming was more frequent and greatest on terminal shoots of branches with a south to southwest aspect. The maximum rise above ambient air temperature exceeded 20 degrees C, and the maximum one minute decrease in temperature was 9 degrees C, with maximum rates of 0.8 and 0.6 degrees C min(-1) sustained over 10- and 15-min intervals, respectively. These data demonstrate that red spruce is subject to rapid temperature fluctuations similar to those known to produce visible injury in American aborvitae, a much hardier species. We concluded that solar warming to temperatures above the freezing point was unlikely to result in dehardening and subsequent freezing injury, because warming was infrequent, of short duration, and did not always raise needle temperature above the freezing point. Parts of branches and some individual shoots were frequently covered by snow or rime that may have prevented injury by reducing the frequency or intensity of needle temperature fluctuations. Radiation load on exposed shoots may have been increased by reflection of short wave radiation from snow and rime deposits on surrounding surfaces, which would exacerbate temperature fluctuations.     

Seasonal air and soil temperature effects on photosynthesis in red spruce (Picea rubens) saplings

Net photosynthesis and stomatal conductance were measured in ten red spruce (Picea rubens Sarg.) saplings, growing near Ithaca, New York, throughout the early spring and late-fall growing periods. Gas exchange and daily minimum and maximum soil and air temperatures were also measured. Linear regression analysis showed that rates of net photosynthesis were positively correlated with both minimum daily soil and air temperatures but that minimum soil temperature was a better predictor of net photosynthesis. Moreover, net photosynthesis was more sensitive to changes in soil temperature than to changes in air temperature, and photosynthesis was approximately twice as sensitive to temperature changes during the fall than during the spring.     

Calcium addition at the Hubbard Brook Experimental Forest increases sugar storage, antioxidant activity and cold tolerance in native red spruce (Picea rubens)

In fall (November 2005) and winter (February 2006), we collected current-year foliage of native red spruce (Picea rubens Sarg.) growing in a reference watershed and in a watershed treated in 1999 with wollastonite (CaSiO(3), a slow-release calcium source) to simulate preindustrial soil calcium concentrations (Ca-addition watershed) at the Hubbard Brook Experimental Forest (Thornton, NH). We analyzed nutrition, soluble sugar concentrations, ascorbate peroxidase (APX) activity and cold tolerance, to evaluate the basis of recent (2003) differences between watersheds in red spruce foliar winter injury. Foliar Ca and total sugar concentrations were significantly higher in trees in the Ca-addition watershed than in trees in the reference watershed during both fall (P=0.037 and 0.035, respectively) and winter (P=0.055 and 0.036, respectively). The Ca-addition treatment significantly increased foliar fructose and glucose concentrations in November (P=0.013 and 0.007, respectively) and foliar sucrose concentrations in winter (P=0.040). Foliar APX activity was similar in trees in both watersheds during fall (P=0.28), but higher in trees in the Ca-addition watershed during winter (P=0.063). Cold tolerance of foliage was significantly greater in trees in the Ca-addition watershed than in trees in the reference watershed (P<0.001). Our results suggest that low foliar sugar concentrations and APX activity, and reduced cold tolerance in trees in the reference watershed contributed to their high vulnerability to winter injury in 2003. Because the reference watershed reflects forest conditions in the region, the consequences of impaired physiological function caused by soil Ca depletion may have widespread implications for forest health.     

杨树品种变温胁迫试验及抗冻性评价

采用模拟自然界冬季温度变化的某些特征,用不同的低温和变温条件对不同杨树品种1年生休眠苗木和离体材料进行胁迫,旨在研究低温和变温对杨树发生冻害的影响,同时在试验结果基础上,对不同品种的抗冻性作出初步评价.试验结果显示,持续的低温对不同杨树具有一定的伤害,但高温和低温的变温对不同杨树伤害更大,而且变化幅度越剧烈,造成伤害越严重;从参试品种(种)试验结果分析得出,马氏杨、小叶杨、小黑杨、辽胡杨、小美旱杨、青山杨抗性较好,中绥12杨、辽宁杨、荷兰3016杨、沙兰杨抗性中等,欧美108杨、丹红杨抗性最差,与生产应用结果基本一致.     

Effects of seed water content and storage temperature on the germination parameters of white spruce, black spruce and lodgepole pine seed

The effect of seed water content (WC) (2–3, 5–6 and 22–25%, on a fresh weight basis), storage temperature (+4, −20, −80 and −196°C) and storage duration (6, 12, 24, 48 and 60 months) on the germination of white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) B.S.P.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed was investigated. Germination of white spruce control (untreated) seeds and seeds adjusted to 2–3% and 5–6% WC declined after 48 months of storage at −80 and −196°C, with a further decline at 60 months at −20, −80, −196°C. Germination remained high when control white spruce seeds and seeds with 2–3, 5–6% WC were stored at +4°C, over all storage durations. Generally, black spruce and lodgepole pine exhibited high germination at all storage temperatures at 2–3% and 5–6% WC as well as the control (untreated) seed, for up to 60 months in storage. Germination declined for all three species when seed was conditioned to 22–25% WC. This loss in germination was partially recovered in white spruce seed stored at +4, −20 and −80°C after storage durations of 24, 12 and 48 months, respectively, and in black spruce seeds stored at −20 and −196°C after storage durations of 24 months. Mean germination time (MGT) was relatively constant for all species, under all conditions, except for seed conditioned to 22–25% WC, where MGT increased for white spruce seed stored 48 months at −80 and −196°C, and for black spruce seed stored 24 months at +4 and −80°C and 60 months at −196°C. These results show that the optimal storage temperatures are 4°C for white spruce, and 4, −20, −80, and −196°C for black spruce and lodgepole pine, and 2–6% water content is optimal for all 3 species at these temperatures.     

Accretion, partitioning and sequestration of calcium and aluminum in red spruce foliage: implications for tree health

Calcium (Ca) is an essential macronutrient in plants and is an important component of many cellular structures and physiological processes as well as overall forest function. Aluminum (Al) in soil solution can inhibit Ca uptake by plants and disrupt many Ca-dependent metabolic and physiological processes of plants. The ratio of Ca to Al in soil solution can be an important indicator of forest health, especially on acid soils. We used sequential chemical extractions (water, acetic acid and hydrochloric acid) to assess the chemical availability of Ca and Al in foliage from mature red spruce (Picea rubens Sarg.) trees growing under ambient environmental conditions. In plants deficient in Ca and with intermediate total foliar Ca concentration ([Ca]), Ca preferentially accrued in labile and physiologically available forms (water- and acetic acid-extractable). In plants with total foliar [Ca] above a "sufficiency" threshold, Ca also accrued in a chemically sequestered form with low solubility (HCl-extractable), suggesting that Ca sequestration is an inducible process in response to excess foliar Ca. Because it has low solubility, it is likely that sequestered Ca is unavailable for Ca-dependent physiological processes. Immobilization of Al in foliage was related to Ca sequestration, suggesting that Ca sequestration may provide a passive mechanism for Al tolerance in the foliage of these trees. Aluminum immobilization was evident based on the ratio of HCl-extractable Al to the more labile (water- and acetic acid-extractable) forms of Al. Sufficient labile Ca combined with Al sequestration was associated with plant health, including enhanced foliar accretion of Mg and Mn, greater tree growth, enhanced foliar cold hardiness and reduced winter injury. These findings demonstrate that not all chemical forms of foliar Ca and Al are of equal physiological significance and underscore the importance of assessing the biologically significant element forms in biogeochemical research.     

Rapid freezing injury in red spruce: seasonal changes in sensitivity and effects of temperature range

On calm, cold days in winter, sun-exposed needles of red spruce (Picea rubens Sarg.) may warm 10 to 20 degrees C above ambient air temperature, and undergo rapid (>/= 1 degrees C min(-1)) fluctuations in temperature as light breezes or passing clouds alter the energy balance of the foliage. It has been proposed that the resulting rapid freeze-thaw cycles (freezing stress) cause a type of winter injury in montane red spruce that is characterized by necrosis of sun-exposed foliage. In autumn and winter, we monitored rapid freezing stress response of needle sections from 10 montane red spruce trees by subjecting needles to rapid freezing over the temperature span typically recorded in the field. In autumn, experimental rapid freezing stress produced severe injury only at temperatures considerably lower than expected for that time of year. In winter, rapid freezing caused occasional, moderate injury in fully hardened foliage of trees susceptible to both slow and rapid freezing. Seasonal changes in sensitivity to rapid and slow freezing were correlated, suggesting that environmental factors that are known to affect sensitivity to slow freezing may also affect sensitivity to rapid freezing. Experimental manipulation of the start and end temperatures of rapid freezing stress events showed that moderate to severe needle injury can occur in susceptible trees at temperature spans slightly more extreme than those typically recorded in the field. The extent of injury was similar at different starting temperatures if rapid freezing occurred over the same temperature span. Year-old foliage was consistently less sensitive to rapid freezing stress than current-year foliage, but some year-old foliage was damaged when the rapid freezing stress regime caused severe injury in current-year foliage. We conclude that rapid freeze-thaw cycles can explain light to moderate injury of current-year foliage, but they do not explain the more severe and widespread pattern of foliar damage that has occurred intermittently over at least the last 18 years.     

Effects of cold storage and water stress on water relations and gas exchange of white spruce (Picea glauca) seedlings

To determine the effects of lifting time and storage on water-stress resistance of nursery-grown white spruce (Picea glauca (Moench) Voss) seedlings, we compared gas exchange, water relations and mortality of 3-year-old seedlings lifted in October 1991 and stored at -2 degrees C for 3 months with seedlings lifted in January 1992. The seedlings were placed in nutrient solution and subjected to -1.1 or -2.7 MPa water stress induced by polyethylene glycol 3350 for 9 days. Water stress, but not lifting time, had a significant effect on seedling net assimilation, symplastic volume and turgor loss point. In a second experiment, seedlings lifted in October 1991 were stored at -2 degrees C for 7 months and compared with seedlings lifted in May 1992. The seedlings were planted in pots, and their gas exchange and water relation parameters measured in response to gradual water stress. The results suggest that prolonged cold storage retards photosynthetic recovery of seedlings after planting. Higher rates of net assimilation in seedlings lifted in May were not directly related to their water status. Nonstomatal limitations were the primary factor influencing photosynthetic rate. We conclude that the inferior ability of cold-stored seedlings to tolerate water stress was due to poor osmotic adjustment and a lag in recovery of photosynthesis.     

低温胁迫对仁用杏花器官抗寒性的影响

以仁用杏花瓣、雄蕊、雌蕊为试材,测定了低温胁迫条件下花器官细胞渗透调节物质含量变化,及低温不同持续时间条件下花器官抗氧化系统的变化。结果表明:随温度下降,花器官可溶性蛋白、可溶性糖含量随温度下降先增加后下降,脯氨酸含量则保持增加趋势;低温作用时间的延长使膜透性、膜脂过氧化产物MDA含量增加,处理时间每增加0.5 h,花瓣、雄蕊、雌蕊细胞膜透性平均增加,MDA含量平均增加3.35 nmol/gFW4、.83nmol/gFW、5.98 nmol/gFW,花器官SOD和POD酶活性在温度高于-4℃条件下,随着温度下降和持续时间延长而上升。低温持续时间延长对花器官的伤害与温度下降的效果相似。花器官抗寒能力顺序为花瓣雄蕊雌蕊。     

Influence of water stress on the physiology and growth of red spruce seedlings

Two-year-old, container-grown red spruce (Picea rubens Sarg.) seedlings from a New Hampshire seed source were exposed to 10 or 11 drying cycles in which the seedlings were not watered until their midday (1400 h) xylem water potentials averaged -1.57 MPa. Control seedlings were kept well watered to maintain midday water potentials of about -0.73 MPa. After the final drying cycle, the water-stressed seedlings were rehydrated and osmotic potentials were determined by pressure-volume analysis. Gas exchange at ambient CO(2) concentration (338 ppm) and at an elevated CO(2) concentration (838 ppm) was measured on both groups of plants as they slowly dried down. No osmotic adjustment or photosynthetic acclimation occurred as a result of the water-stress treatment and both groups of seedlings maintained photosynthesis to water potentials as low as -3.0 MPa. Twenty-four hours after rehydration, the water-stressed seedlings had photosynthetic rates as high as the control seedlings. Estimated stomatal limitation to photosynthesis was approximately 30% down to water potentials of -1.4 MPa, but increased steadily as water potentials decreased further. At ambient CO(2) concentrations (338 ppm) and water potentials averaging -2.45 MPa, photosynthetic rates of water-stressed seedlings were 15% those of well-watered seedlings, whereas when the same water-stressed seedlings were measured in the presence of an elevated concentration of CO(2) (838 ppm) their photosynthetic rates were 73% those of well-watered seedlings measured at an ambient CO(2) concentration (338 ppm).     

Cold tolerance of black spruce,white spruce,jack pine,and lodgepole pine seedlings at different stages of spring dehardening

New Forests - Understanding tree vulnerability to freezing temperatures will help resource managers to mitigate the effects of climatic variability. To test the effectiveness of tissue dehardening...     

Effects of mist acidity and ambient ozone removal on montane red spruce

Recent forest studies have established that high-elevation (> 900 m) populations of red spruce (Picea rubens Sarg.) in the northeastern USA are declining. Because it has been suggested that changes in air quality are responsible for the decline, we examined the effects of acidic mists and ozone on several biochemical and growth parameters in mature montane red spruce. We used branch-sized environmental chambers to introduce mists of controlled composition and exclude ambient clouds and ozone from individual branches within a tree. Mists consisting of distilled water increased the end-of-season pigment concentration and shoot length of enclosed branches relative to ambient or artificial mists. Needle and twig weights and starch concentrations were not significantly altered by the acidic mist treatments. Removal of ambient ozone had no apparent effect on the variables measured.     

Effects of temperature and sulfonation on shear deformation of spruce wood

Summary The effects of temperature and sulfonation on the deformation of spruce wood at conditions comparable to those during screw press impregnation prior to mechanical pulping were studied using a dynamic testing method. In addition to the physical properties of wood, shear fracture surfaces obtained at different deformation temperatures and at different sulfonation levels were studied using scanning electron microscopy (SEM).The results showed that the failure energy of wood decreased gradually with increased deformation temperature in the tested range of 20–95 °C, due to thermal softening of the material. In addition to thermal treatment, the failure energy could also be reduced by sulfite treatment of the wood before deformation, and decreased with increasing sulfonation degree.The SEM analysis showed that increasing the deformation temperature causes the fracture plane to travel around the fiber walls instead of through them, thus exposing a smoother wood surface with less fiber damage. At a given deformation temperature, particularly at the lower temperatures, sulfonation improves fiber separation.Financial support from the Swedish National Board for Industrial and Technical Development (NUTEK) is gratefully acknowledged     

Effects of nutrition and soil water availability on water use in a Norway spruce stand

We investigated effects of nutrition and soil water availability on sap flux density, transpiration per unit leaf area (EL), and canopy stomatal conductance (GS) of Norway spruce (Picea abies L. (Karst.)) in northern Sweden during the 1996 growing season. Our objectives were to determine (1) if artificially imposed drought (65% rain diversion) reduces soil water sufficiently to cause physiological limitations to whole-tree and plot-scale water transport, and (2) whether increased capacity for water transport resulting from fertilization-induced increases in leaf (> 3-fold) and sapwood areas (> 2.3-fold) deplete soil water sufficiently to cause a negative feedback on GS and EL. We monitored soil water content (theta) and soil water potential (PsiS) in control (C), drought (D), fertilized (F) and irrigated + fertilized (IL) treatment plots, along with site meteorological conditions. Ten trees per plot were monitored for sap flow. Although there were significant treatment differences in mean daily EL (C > D > F; P < 0.01) and GS (C > D > F; P < 0.05), variation in absolute magnitudes was small. Therefore, transpiration differences on a unit ground area basis (EC) were nearly proportional to leaf area differences. Precipitation was well distributed throughout the study period and so PsiS remained high, except during short dry periods in Plot F when it declined rapidly. Thus, although soil water was not limiting to GS, EL or EC when precipitation was uniformly distributed throughout the growing season, we cannot conclude that water availability would not limit GS in fertilized stands if the seasonal distribution of precipitation were altered.     

低温胁迫对我国北方地区引种的无花果抗寒性的影响

为给无花果抗寒能力的评价与抗寒品种的选育提供参考依据,以我国北方地区引种的14个无花果品种为研究对象,采用人工低温(0~-20℃)处理对其1年生枝条进行了胁迫试验,并对其相对电导率、可溶性蛋白含量、可溶性糖含量、脯氨酸含量、SOD活性、POD活性和MDA含量进行了测定,还根据相对电导率和对应的低温温度,依据logistic方程,建立了回归模型,对14个无花果品种的抗寒性进行了综合评价。结果表明:依据半致死温度来评价,布兰瑞克、ALMA等品种的抗寒性均较强,-5~-10℃的低温会严重影响参试的大部分品种的生存和生长发育;其SOD和可溶性糖在-10℃时的测定值是反映无花果抵抗和适应低温能力的一个临界值,而可溶性蛋白和POD的临界值是在处理温度为-5℃时的测定值。部分品种的综合抗寒能力的评价结果与其半致死温度的测定结果存在差异,但新早黄、ALMA、金傲芬和紫蕾等品种均具备较好的抗寒潜力。     

Effects of water vapour heating on structure and properties of cork

Summary The effects of heating cork in water vapour at 100°C and 300°C are studied and compared with those produced by heating in air at the same temperatures. Dimensional and mass changes were measured and radial compression curves were obtained following various treatments. The 300°C treatments originate a straightening of the originally corrugated cell walls, while the cell wall material undergoes thermal degradation. Larger swellings and larger mass changes are observed in the treatments in water vapour as compared to those in air. The 100°C treatments do not induce degradation and produce reversible changes in technological properties which are simply due to differences in the water content.     

Long-term growth trends of red spruce and fraser fir at Mt. Rogers,Virginia and Mt. Mitchell,North Carolina

Cross-sectional area growth and height growth of Fraser fir and red spruce trees growing in Virginia and North Carolina were analyzed to identify possible long-term growth trends. Cross-sectional area growth provided no evidence of growth decline. The individual discs were classified according to parameter estimates of the growth trend equation. The predominant pattern of growth was a steady increase followed by fluctuation about a horizontal line. Other cross-sections exhibited a steady increase throughout the series. The only discs that represent declining growth patterns were from trees in subordinate crown position or which had previous top damage. No unexplained growth decline was present in any disc. The results regarding height growth were uncertain. A slight decline in height growth was present although we suggest that this observation was due to problems with the data or the model used to fit height growth. These findings contradict other studies suggesting that a recent growth decline has occurred in red spruce in the southern Appalachians.     

The effects of soil and air temperature on CO2 exchange and net biomass accumulation in Norway spruce, Scots pine and silver birch seedlings

Soil temperature is proposed to affect the photosynthetic rate and carbon allocation in boreal trees through sink limitation. The aim of this study was to investigate the effect of temperature on CO(2) exchange, biomass partitioning and ectomycorrhizal (ECM) fungi of boreal tree species. We measured carbon allocation, above- and below-ground CO(2) exchange and the species composition of associated ECM fungi in the rhizosphere of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies K.) and silver birch (Betula pendula Roth) seedlings grown in soil maintained at 7-12, 12-15 and 16-22 °C. We found increased root biomass and photosynthetic rate at higher soil temperatures, but simultaneously with photosynthesis rate, higher temperature generally increased soil respiration as well as shoot, and root and rhizosphere respiration. The net CO(2) exchange and seedling biomass did not increase significantly with increasing temperature due to a concomitant increase in carbon assimilation and respiration rates. The 2-month-long growth period in different soil temperatures did not alter the ECM fungi species composition and the below-ground carbon sink strength did not seem to be directly related to ECM biomass and species composition in any of the tree species. Ectomycorrhizal species composition and number of mycorrhiza did not explain the CO(2) exchange results at different temperatures.     

低温胁迫对蓝莓枝条呼吸作用及生理生化指标的影响

为明确蓝莓枝条不同部位的耐低温能力,利用人工模拟低温胁迫的方法研究了蓝莓1年生枝条尖端、1年生枝条基端和2年生枝条对低温胁迫的生理响应。结果表明:低温胁迫下蓝莓不同部位枝条的各生理指标之间虽然具有一定的相关性,但不同生理指标的相关系数差异较大,即蓝莓枝条不同生理过程对低温的敏感性明显不同。其中,0℃时1年生枝条特别是其尖端的呼吸速率明显高于2年生枝条,但其呼吸作用对低温也特别敏感,当温度降低到-10℃时即均发生明显的降低,且1年生枝条尖端的降低幅度最大。另外,低温胁迫下1年生枝条尖端的丙二醛(MDA)含量和相对电导率增加幅度也明显大于1年生枝条基端和2年生枝条,即1年生枝条尖端对低温胁迫更为敏感。低温胁迫下不同部位枝条虽可以通过增加可溶性糖(SS)和可溶性蛋白(SP)等渗透调节物质,以及增强SOD和POD等抗氧化酶活性的方式来提高其抗寒能力,但当温度降低到-40℃时,不但抑制了蓝莓1年生枝条尖端可溶性蛋白的合成,并且1年生枝条尖端和基端的SOD活性较-20℃时也有不同程度的降低,即-40℃时1年生枝条特别是其尖端蛋白质合成的抑制以及抗氧化酶活性的降低可能是导致其蓝莓在我国北方大兴安岭地区易发生冻、干梢现象的主要原因。而1年生枝条基端和2年生枝条具有较强抗低温能力的原因除了其本身代谢活性较低,对低温不敏感外,低温下有效积累渗透调节物质和增强抗氧化酶的活性在降低其膜质过氧化程度和电解质外渗方面发挥了重要的作用。